feat: CountDownLatch使用

multithreading1/src/main/java/cn/bunny/atomic/AtomicExample04.java

@@ -1,4 +1,24 @@
 package cn.bunny.atomic;
 
+import java.util.concurrent.CountDownLatch;
+
 public class AtomicExample04 {
+    public static void main(String[] args) throws InterruptedException {
+        CountDownLatch latch = new CountDownLatch(2);
+        // 此时为1
+        latch.countDown();
+        System.out.println(latch.getCount());
+        
+        // 此时为0
+        latch.countDown();
+        System.out.println(latch.getCount());
+
+        // 还是为0
+        latch.countDown();
+        System.out.println(latch.getCount());
+
+        latch.await();
+
+        System.out.println(latch.getCount());
+    }
 }